BaseWicketTester.StartComponentInPage

getMarkup

Get the Markup associated with the Component. If not subclassed, the parent container is
asked to return the markup of this child component.

Components like Panel and Border should return the "calling" markup fragment, e.g.
<span wicket:id="myPanel">body</span>. You may use
Panel/Border/Enclosure.getMarkup(null) to return the associated markup file. And
Panel/Border/Enclosure.getMarkup(child) will search the child in the appropriate markup
fragment.